The aim of this study is to compare and contrast the response of natural abutment teeth connected rigidly or non-rigidly to osseointegrated dental implants. Clinically significant criteria including bone loss and mobility of the teeth and implants will be used to evaluate these two treatment options, in order to subsequently aid the dentist in selecting methods of implant attachment to natural dentition. An experienced team of three Oral and Maxillofacial Surgeons, six Prosthodontists and one Periodontist will be assigned patients such that all evaluations of the teeth and implants are blinded, and not evaluated by the surgeon and prosthodontist who placed and restored the implants. In addition, the periodontist is now added to the team in order to evaluate all of the patients. A statistician has been involved with the design of this study and will participate as a co-investigator. Fifty patients will be selected based on their need for bilateral mandibular distal extension bridges articulating against a complete maxillary denture. One 10 mm. long Integral implant will be placed in the right and left mandibular first molar regions. Twelve weeks later, the implants will be restored with three unit bridges, with natural abutment teeth rigidly or non-rigidly attached to the implant evaluation. Prior to and following bridge insertion, radiographs, soft tissue pockets, bleeding and plaque indexes, tooth and implant mobility, and general clinical quality will be assessed every six months from the time of implant placement for five years. All patients will be entered into the study by the end of year three. A renewal application will be submitted to enable long term follow-up. Several NIDR consensus conference speakers requested NIH support for prospective studies on different treatment modalities for partially edentulous patients. We seek clinically significant information.